1. Field of the Invention
The invention presented herein relates to apparatus for transferring images of electronically conductive toner powder from the surface of a member to the surface of another member.
2. Description of the Prior Art
In recent years electrostatic copy machines have been developed which employ a developing powder that is carrierless in that no carrier particles are included and only electronically conductive toner powder is used to develop an electrostatic image. Such powders are also used in styli printing apparatus. While there are advantages to the use of electronically conductive toner powder for the forming of images, problems are presented with respect to the transfer by electrical means of such images to another surface. In the case of transfer to plain paper, it is proposed that the paper be pre-dried since the quality of the transfer has been found to be dependent upon the moisture content of the paper. Another approach to avoid the conductivity problem presented by humidity variations in the copy paper involves treatment of the paper to provide a resin coating on a surface of the paper to present a surface that is lower in conductivity. Another approach is to position the image bearing support so it contacts the support to which the toner image is to be transferred and use a dielectric liquid to wet the support on which the powder image is to be transferred with the transfer being aided by a high d.c. voltage that is maintained between the image bearing support and the support to which the toner image is to be transferred. This approach complicates the apparatus in that a mechanism must be used for applying the liquid. In addition, the apparatus must provide for the drying of the copy support to remove the dielectric liquid after the transfer has been made. Odor can also be a problem.